U.S. Pat. No. 4,482,347 discloses a peristaltic pump which, because of its compactness and simplicity of construction, and its precise, accurate, and reliable operation, is particularly suitable for medical use. The pump includes a series of roller assemblies each having concentric inner and outer bearing members capable of free rotation with respect to each other. The inner members are concentrically mounted on a power drive shaft with the centers of the inner members equidistant from the axis of the shaft and spaced at uniform angular distances thereabout to describe a helix about the axis of the drive shaft. A resilient tube extends along a line parallel with the shaft and is supported by a platen so that the tube is sequentially compressed by each of the outer bearing members of the series of roller assemblies, thereby driving fluid through the resilient tube. A thin elastomeric membrane is interposed between the outer bearing members and the tube with the membrane in continuous contact with the tube during pump operation.
The outer surface of each outer bearing member of U.S. Pat. No. 4,482,347 is of uniform diameter for its full axial extent--that is, the outer surface appears as a straight line when each roller assembly is viewed in longitudinal (axial) section. In the construction of other types of pumps, particularly pumps in which rollers are urged lengthwise along compressible fluid-carrying tubes, it has been known to utilize rollers with contoured surfaces for improving tracking and for other purposes. Thus, U.S. Pat. No. 3,567,345 discloses a rotary pump having rollers with depressions 32, and U.S. Pat. No. 4,229,299 discloses a similar rotary pump having rollers with convex surfaces 300, 306.
U.S. Pat. No. 4,373,525 discloses a peristaltic pump with reciprocating fingers that engage a tube supported by a spring-loaded pressure plate. Each of the fingers is in the form of a rectangular plate (FIG. 3) having a rounded lower edge when viewed in elevation (FIG. 1).